The present invention relates to a light hardening device as well as a method for polymerization of polymerizable masses. Light hardening devices of this type are used, for example, if light polymerizable masses or material are to be hardened in a focused manner.
The polymerizable materials which can be hardened by light hardening devices, as is conventionally known, are, for example, cements, an excess amount of which must be applied to complete the application task. The oversupply or excess amount of cement is extremely hard after the complete hardening of the mass or material, and a high degree of effort is required in order to remove this excess material with suitable dental instruments such as, for example, by milling. Moreover, the removal of hardened excess material causes a high wearing away of the scraping or sharpening instruments or, respectively, the milling instruments.
It has been proposed, for example, to use two photo initiators, which have different spectral sensitivity maximums, and to harden the mass or material completely with lamps or lights having the corresponding emission spectrum.
It has further been proposed in the prior art, with respect to photo polymerizable materials which comprise two different photo initiators, to initially activate the first photo initiator by irradiation thereof by an appropriate wavelength so as to thereby partially harden the material, to thereafter remove the excess material, and subsequently, via a second photo initiator, to undertake the complete hardening of the material. Such systems have, however, not found full acceptance due to the considerable effort required to deploy two photo initiators and the switching over work required to switch between the double systems to effect the partial hardening of the material is difficult to control. Therefore, the excess material is typically removed after the complete hardening of the material which requires, however, a considerable effort.
The present invention offers a solution to the challenge of providing a light hardening apparatus as well as a method for polymerization which permits the realization of an improved material cohesiveness to be achieved by light hardening while nonetheless offering more flexibility to use different polymerizable masses or material.
The light hardening device of the present invention, or, respectively, the inventive method, uses simple means to offer the possibility to completely harden the polymerizable mass or material in a step-wise manner whereby, in the first step, a partially polymerized, easily workable material is created and, in a second step, the finished, completely hardened material is created.
In accordance with the present invention, it is particularly advantageous that a removal of the excess material is possible in spite of the sole use of a single photo initiator to realize a partial polymerization. In this connection, a spectral overlapping between the emission spectrum of a light emitting diode and the sensitivity spectrum of the photo initiator is used to advantage. It is particularly advantageous, in this connection, that one can also work with commercially available, cost favorable dental masses or materialsxe2x80x94that is, no special masses or materials requiring two photo initiators need be used. This provides a significant cost advantage alone for the reason that the photo polymerizable masses or material can be polymerized with solely a single photo initiator which can be manufactured in a standardized manner in comparatively large amounts, which leads to significant cost savings with respect to the production and storage of such material. In contrast, special masses are substantially more difficult to work with and more expensive for the reason alone that the storability or shelf life of such special masses is not unlimited.
In contrast, it is particularly advantageous that the light hardening device of the present invention is able to effect polymerization of a photo polymerizable mass or material with solely a single photo initiator. In accordance with the present invention, a system comprising a single light hardening apparatus or device can be used in combination with the photo polymerizable mass or material.
Surprisingly, it has been discovered that the partial overlapping between the emissions spectrum of the first light emitting diode and the sensitivity spectrum of the photo initiator provides the possibility to achieve a partial hardening of the mass or material in a manner such that, during a pause in the hardening process, excess material can be removed while not foreclosing undertaking a further hardening following the pause in the hardening process.
The relationship between the intensities of the light output during the first time period and the light output during the second time period can be accommodated to a wide range of requirements as can the duration of the first and second time periods as well. Advantageously, the emissions intensity of the first light emitting diode is set at at least 100 mW/cm2 while the light intensity of the light emitting diode is set at at least 300 mW/cm2 and is preferably set at 600 to 1,000 mW/cm2. In connection with a high light intensity of the first light emitting diode and/or a relatively long first time period, the partially polymerized material is somewhat firmer so that the removal of excess material can also be undertaken mechanically with commercially available dental instruments while, in connection with a relatively lower light intensity and/or a relatively shorter first time period, a sculpting or, respectively, a working of the mass or material can be undertaken.
It is, in any event, important that the spectrum of the first light emitting diode and the sensitivity of the photo initiator are clearly differentiated from one another and, especially, that the maxima of the two parameters have clearly differentiated wavelengths.
Preferably, the intensity maximum of the first light emitting diode is chosen such that its wavelength is greater than the wavelength of the sensitivity maximum of the photo initiator. For example, camphor quinone can be used as a photo initiator and the first light emitting diode can be configured as a green light emitting diode. The wavelength maxima values are then between around 470 and 505 nanometers; therefore, the wavelength is clearly different than that of the photo initiator.
In accordance with a particularly advantageous configuration of the present invention, the second light emitting diode is chosen such that its emission maximum coincides with the sensitivity maximum of the photo initiator while, at the same time, the spectrums are, to the greatest extent possible, coincidental with one another.
It is to be understood, however, that in lieu of a light emitting diode or a plurality of light emitting diodes, at least one group of LEDs or, respectively, so-called pads, can be deployed. U.S. patent applications 10/139,308, 10/139,308, and 10/177,014 are, in this regard, fully incorporated by reference herein.